The combining of two or more liquids together to form a defined mixture of the constituent liquids is fundamental to many industrial processes and commercial products. This combining of liquids may be referred to as batching or blending and is common to many industrial segments including pharmaceutical products, biomedical products, food processing products, household products, personal care products, petroleum products and lubricants, chemical products, and many other general industrial, commercial, and consumer liquid products.
Most typically, liquid products are made by combining relatively large quantities of each constituent. Constituent liquids are held in large tanks and are moved in correct volumetric or weight ratio into another large tank where mixing of the liquids occurs. This general process is referred to as batching.
The many drawbacks and limitations of liquids batching are well detailed and discussed in U.S. Pat. No. 6,186,193 B1, column 1, line 47, to column 2, line 7. These discussions are thus incorporated into this specification by reference.
Because of the numerous and substantial shortcomings and limitations of liquid products batch processing, alternative means of liquid products manufacturing have been sought. One alternative method to batching is termed continuous stream blending.
Continuous stream blending embodies the notion of combining constituent liquids to form a liquid product only as needed or on a demand basis. Essentially, product is made only as required and at the flow rate required. The flow rate required is typically based on the demand of the liquid filling machine packaging the liquid product, or by the process or utilization demand or consumption rate of the blended liquid product.
The appeal and merit of a continuous stream blending system, as distinct from a batching system, is clear. The ability to eliminate large liquid product batch preparation and holding tanks leads to a small system volume, more product compounding flexibility, faster product species turnaround, smaller and shorter practical packaging run capabilities, and a substantially lower capital asset commitment. Continuous stream blending can also yield superior product formula accuracy and quality, and can eliminate the barrier or “wall” between liquid products processing and liquid products packaging, as well as greatly reduce waste, cleanup time, and effluent volumes. Furthermore, mixing is simplified and product aging effects are largely eliminated. The real issue is how to build a continuous stream blending system with the maximum degree of accuracy, flexibility of use, and versatility of application in a broad range of commercial sectors, and with the best possible simplicity of design and function and ease of use.
The numerous designs for continuous stream blending that have been previously disclosed in the commercial and patent art are set forth in substantial detail in U.S. Pat. No. 6,186,193 B1 at column 2, line 36, to column 4, line 16. The problems and limitations of these designs are also therein reviewed. This section of U.S. Pat. No. 6,186,193 B1 is thus incorporated into the present specification by reference.
The prior art also includes U.S. Pat. No. 6,186,193 B1, in which Phallen et al disclose an invention consisting “of a method and apparatus providing for the continuous stream blending, preferably on a mass ratio basis, of two or more liquids. Each individual liquid stream is synchronously dosed in precise mass ratio to a common mixing point. The flow of each stream is on-off or digital. Repeated mass ratio doses of defined and matching flow interval, referred to as synchronous digital flow, interspersed with a defined interval of no flow, constitutes digital flow at a net rate sufficient to meet or exceed some required take-away of the blended liquids. In one preferred embodiment, each dose stream flow is produced and measured by an apparatus preferably consisting of a device for initiating liquid flow in the form of a controller and a servomotor-driven precision positive displacement pump, the apparatus further including a Coriolis mass meter and a precision flow stream shut-off device. The servomotor and controller establish and control a periodic and intermittent flow rate necessary to displace a defined mass dose in a precisely defined flow interval. The flow interval is measured against a precision millisecond digital clock. The Coriolis mass meter is used only to totalize mass flow to define the desired mass dose during the defined digital flow interval. The flow stream shut-off device ensures precise delivery of the mass dose to the common mixing point. “The flow rate of a stream is automatically adjusted by the control electronics until the required mass dose is delivered in the defined flow interval” (column 7, line 41 to line 67):                “Because each flow stream starts and stops simultaneously regardless of the mass dose associated with each stream, blending or mixing of the streams at a common intersection to a defined mass ratio formula is facilitated by the simultaneous and kinetic collision and resultant mixing of the coincident flows in a mixing chamber. The blending apparatus can be started at will and can be stopped at the end of each defined dose interval, typically every 5000 mS. This method allows the apparatus to be operated in liquids process environments where frequent stop and start conditions are prevalent, without any penalty or error in mass ratio accuracy or blending efficacy. Use of PLC or PC system control in conjunction with a precision millisecond (1000 Hz) clock signal allows automatic establishment of a mass dose and flow stream synchronization at start up, as well as self-checking and correction of mass dose and flow synchrony with each digital flow cycle. Operation is preferably based upon a mass ratio recipe or formula, although the control software also provides for conversion of volumetric formulas to mass. The apparatus automatically adapts to changes in take-away flow rate by varying the off time or no flow interval between synchronous digital doses, thus eliminating manual or electronic adjustment or recalibration of the liquid flow streams as take-away demand varies” (column 8, line 1 to line 24).        
In U.S. Pat. No. 6,186,193 B1, Phallen teaches a continuous stream blending design in which first stage streams mixing occurs by hydraulically combining the streams in a kinetic mixing chamber, with second stage streams mixing occurring by hydraulic flow and displacement of the streams from the kinetic mixing chamber through a second mixing device which is, in turn, hydraulically connected to a finished blend tank.
In Phallen's invention, the motive force to move the liquids into and through the kinetic mixing chamber and through a mixing device and onward into the finished blend tank, is derived solely from the streams ratio dosing pumps. Essentially, the combined pumped flow from all of the stream pumps supplies all of the energy to move the liquid streams to and through the combining and blending portions of the apparatus and, after streams combining, on through the connecting conduit into the terminus of the system represented by the finished blend tank. In the Phallen design there is no other or additional pump or other motive force inducing liquid flow through the apparatus (see FIG. 3 of this specification which shows this prior art arrangement).
The hydraulic nature of the Phallen patent is clear. As a hydraulic design, the entire fluid flow pathway, from the bulk supply source tank of each stream to the finished blend tank, is charged with the liquids being combined. There are no intentional gas voids or other breaks in the fluid flow pathway in any part of the system.
Although the design taught by Phallen represents an advancement in the state-of-the-art and has had commercial success, limitations and constraints have emerged.
Among the limitations of the U.S. Pat. No. 6,186,193 B1 invention, the most evident center on the completely hydraulic design of the fluid flow pathway of the apparatus. Because of the hydraulic design, streams flow rates are influenced by changing back pressures, which are, in turn, fundamentally influenced by varying viscosities, rheologies, temperatures, and so forth.
Because the system is hydraulic, every variation or disturbance or change in operating conditions is evident in every other part of the system. Each and every part of the system fluid flow pathway is hydraulically connected, one to the other. Thus, a change in flow on any stream represents an essentially instantaneous change in the flow resistance or back pressure acting on every other flow stream. In effect, every stream is “visible” to every other stream. Thus, each manual or automatic performance adjustment on a given stream acts upon and alters the conditions of flow on the remaining streams. Moreover, the performance change on a given stream is directly contradictory to the setpoint requirements of the other flow streams. Thus, a reduced flow on one stream lowers the overall system hydraulic pressure. This pressure decrease tends to increase dose ratio flow on the remaining flow streams, which then forces a flow rate adjustment to be made on these streams. Conversely, an increased flow on one stream increases the overall system hydraulic pressure. This pressure increase tends to lower dose ratio flow on the remaining flow streams, which then forces a flow rate adjustment to be made on these streams.
In U.S. Pat. No. 6,186,193 B1, Phallen also teaches a design which provides for the ability to sample each stream by direct ratio dose collection to atmosphere at the point of hydraulic combining of each stream into the kinetic mixing chamber. The purpose of this sampling is twofold. First, it provides the means to empirically compare an actual dose mass with the dose mass displayed by the Coriolis mass flow meter, thus proofing the meter and its scaling and calibration. The second purpose of this sampling capability is to provide means to directly measure and verify each dose ratio as delivered into the kinetic mixing chamber. However, with the system in operation, pressure in the kinetic mixing chamber is substantially above atmosphere. This is particularly true with higher viscosity liquids. Because this is true, the sample ratio dose delivered to atmosphere often will not correspond closely to the ratio dose delivered at the higher kinetic mixing chamber pressure when the stream flow rate and delivery time for each condition are held constant. Thus a significant flow rate adjustment must be made for correct dose flow into the kinetic mixing chamber, and direct empirical sampling is not possible.
Another limitation of the Phallen invention is a direct consequence of the hydraulic design. Because the streams pumps supply the flow energy to propel each liquid stream through the system all the way to the finished blend tank, the back pressure on the overall system and upon each stream is determined by the flow structure of the system, principally distal to the streams pumps. The flow structure most prominent in determining this back pressure is the mixing element downstream from the kinetic mixing chamber. In most instances, this mixing element consists of a static mixing device. These types of mixing devices, by their nature, impose a substantial flow restriction and, thus, create a high back pressure. This is particularly true with higher viscosity liquids. Because the stream pumps are the only means of creating flow through the mixing structures of the design, a high or elevated back pressure environment is imposed upon each stream ratio dosing pump. This condition is unfavorable to best ratio dosing accuracy, stability, and repeatability of the ratio dosing pumps. Further, induced back pressures are difficult to predict as a function of changing liquid formulas and constituent liquid components and of changing flow rates and conditions. Changing requirements or conditions relative to liquid viscosities are of particular concern in predicting and controlling system operating pressures.
Another negative aspect of the fluid flow pathway of the Phallen invention is that if additional mixing capability must be added to achieve streams mixing efficacy with a particular liquid formula, back pressures will be substantially increased on all parts of the system, including the streams ratio dosing pumps. This problem can be particularly severe where high viscosity liquids are generally harder to mix together and require more mixing elements for thorough combining. This, in turn, causes a dramatic increase in flow resistance and back pressure acting on the streams ratio dosing pumps.
In U.S. application Ser. No. 11/125,807 filed May 9, 2005, Phallen discloses “An Improved Continuous Liquid Stream Blender” where the problems of interactive streams hydraulic back pressure are overcome by “ . . . use of intermittently operated servo driven pumps, flow meters, and precise fast-acting flow shut-off devices to create repeated time synchronized ratio defined doses of two or more liquids flowing into a common constant pressure streams combining chamber. The synchronized intermittent doses are synchronously removed from the combining chamber at a flow rate matching the summed flow rate of the doses flowing into the chamber and are then displaced through a mixing element” (P1, line 7 to line 13).
In Ser. No. 11/125,807, the ratio doses flowing synchronously into a constant pressure combining chamber are synchronously removed from the chamber by a mix stage pump (P12, line 33 to P13, line 5). This arrangement separates liquid streams ratio combining from streams mixing. Thus, at P13, line 6 to line 25, the inventor states “maintaining the dose streams combining chamber 40 at a constant pressure in order to optimize streams ratio dosing accuracy and stability is achieved by exactly matching the outflow of liquids from the chamber 40 to the streams inflow rates into the chamber. This is done by causing the flow rate from the mix stage pump 42 to exactly match the combining streams ratio dosing flow rate. This flow rate matching, in turn, is generally accomplished by maintaining the combining chamber liquid level at an essentially constant height within the chamber via level controller 36. In addition, component supply levels are also maintained at an essentially constant height by level controllers 28. By this arrangement, the dose stream pressures are optimally low and invariant, while the typically high and less stable back pressures associated with streams mixing are divorced and isolated from the dose streams. Effectively, the mix pump can be sized as necessary to deal with the relatively high mixing back pressure requirements without in any way compromising the desired low pressure optimization of the ratio dosed streams. With this arrangement, there can be no loss of precision in the mechanical combining of the ratio doses. Since there is no flow through the mix pump unless there is matching inflow into the streams combining chamber, the flow streams remain mechanically synchronized in terms of linear flow motion and thus combine in ratio on a flow through basis essentially as though they were directly combined on a hydraulic basis without use of a flow through streams combining chamber” (see FIG. 4 of this specification which shows this prior art arrangement).
The blender invention taught by Phallen in Ser. No. 11/125,807 solves the problems of flow streams ratio dose interaction and divorces flow streams ratio combining from flow streams mixing. Nevertheless, although it represents an improvement in the state-of-the-art and has been commercialized, limitations and constraints associated with the invention have become evident. The solution invented by Phallen involves a three stage blender, consisting of the ratio dosing elements, the combining chamber and mix stage pump, and the final blend tank. Thus, a level of mechanical complexity is found in the combining chamber and mix pump, and in the controls structure and electronics needed to match and maintain the liquids flow into the combining chamber with the mix pump mediated outflow. The extensive addition of apparatus and relatively complicated flow matching controls leads to a much greater economic cost associated with the solution, thus reducing its utility. The additional apparatus used in Phallen's invention to resolve the described problems further impairs the utility of the blender by markedly increasing its system volume and complicating and prolonging the clean-in-place flow sequences, cycles, and volumes needed to clean the blender liquid flow pathways.
With these problems and limitations of the prior art in mind, the present simplified blender invention, and the unique and novel aspects of its embodiments will now be fully discussed and disclosed. In this regard it is a particular objective of the new invention to incorporate and preserve the operable and functional advantages of the digital flow ratio dose blender operating format and associated features and capabilities as set forth by the specification of U.S. Pat. No. 6,186,193 B1 and of pending specification Ser. No. 11/125,807, both of which are thus incorporated herein by reference.